Digital Lighting & Rendering, Second Edition

256 Digital Lighting and Rendering

A shader that allows you to vary the specularity and other parameters

according to the viewing angle of the surface is often called a Fresnel shader.

A Fresnel shader will let you specify a specular color to be seen on parts of

a surface directly facing the camera, and another specular color to be seen

on parts of a surface that are perpendicular to the camera. Besides specular

color increasing at the edge of an object, the specular highlight size and

refl ectivity also increase.

Another way the Fresnel effect can be created is by linking the surface angle

(or facing ratio) of an object to the shader attribute ...